Various precursors are used to form thin films and a variety of deposition techniques have been employed. Such techniques include reactive sputtering, ion-assisted deposition, sol-gel deposition, CVD (also known as metalorganic CVD or MOCVD), and ALD (also known as atomic layer epitaxy). CVD and ALD processes are being increasingly used as they have the advantages of good compositional control, high film uniformity, good control of doping and, significantly, they provide excellent conformal step coverage on highly non-planar geometries associated with modern microelectronic devices.
CVD is a chemical process whereby precursors are used to form a thin film on a substrate surface. In a typical CVD process, the precursors are passed over the surface of a substrate (e.g., a wafer) in a low pressure or ambient pressure reaction chamber. The precursors react and/or decompose on the substrate surface creating a thin film of deposited material. Volatile by-products are removed by gas flow through the reaction chamber. The deposited film thickness can be difficult to control because it depends on coordination of many parameters such as temperature, pressure, gas flow volumes and uniformity, chemical depletion effects, and time.
ALD is also a method for the deposition of thin films. It is a self-limiting, sequential, unique film growth technique based on surface reactions that can provide precise thickness control and deposit conformal thin films of materials provided by precursors onto surfaces substrates of varying compositions. In ALD, the precursors are separated during the reaction. The first precursor is passed over the substrate surface producing a monolayer on the substrate surface. Any excess unreacted precursor is pumped out of the reaction chamber. A second precursor is then passed over the substrate surface and reacts with the first precursor, forming a second monolayer of film over the first-formed monolayer of film on the substrate surface. This cycle is repeated to create a film of desired thickness.
Thin films, and in particular thin metal-containing films, have a variety of important applications, such as in nanotechnology and the fabrication of semiconductor devices. Examples of such applications include high-refractive index optical coatings, corrosion-protection coatings, photocatalytic self-cleaning glass coatings, biocompatible coatings, dielectric capacitor layers and gate dielectric insulating films in field-effect transistors (FETs), capacitor electrodes, gate electrodes, adhesive diffusion barriers, and integrated circuits. Dielectric thin films are also used in microelectronics applications, such as the high-κ dielectric oxide for dynamic random access memory (DRAM) applications and the ferroelectric perovskites used in infrared detectors and non-volatile ferroelectric random access memories (NV-FeRAMs). The continual decrease in the size of microelectronic components has increased the need for improved thin film technologies.
Technologies relating to the preparation of manganese-containing thin films are of particular interest. For example, manganese-containing films have found numerous practical applications in areas such as catalysts, batteries, memory devices, displays, sensors, and nano- and microelectronics. In the case of electronic applications, elemental manganese metal or manganese nitride films can act as barriers layers such that they prevent diffusion of copper interconnects into the underlying silicon dioxide substrate (e.g., self-forming diffusion barrier layers). While barrier layers based on other metal systems may be employed to inhibit copper atom diffusion, there remain significant challenges with such systems. For example, tantalum nitride provides a suitable copper diffusion barrier at film thicknesses greater than about 10 Å—a thickness where such films are continuous—thinner films of tantalum nitride are not continuous, and as such, do not provide adequate diffusion barrier properties. This is a significant hurdle for smaller node devices (less than ˜32 nm) where thinner diffusion barriers are required. Evidence suggests that manganese nitride diffusion barriers may be an attractive alternative to tantalum-based diffusion barriers in the back-end-of-line copper interconnections in next generation devices. However, there are few examples of manganese precursors which can provide high quality and/or high purity films of elemental manganese or manganese nitride. Potential manganese precursor candidates often suffer from poor vapor pressures and reaction rates, and/or provide manganese-containing films with undesirable morphology. Accordingly, there exists significant interest in the development of manganese complexes with performance characteristics which make them suitable for use as precursor materials in vapor deposition processes to prepare manganese nitride and other manganese-containing films. For example, manganese precursors with improved performance characteristics (e.g., thermal stabilities, vapor pressures, deposition rates, and barrier properties of films produced therefrom) are needed, as are methods of depositing thin films from such precursors.